Simulation of gas desorption and geomechanics effects for unconventional gas reservoirs

Hydraulic fracturing of horizontal wells is crucial for economic production of shale gas. Impacts of gas desorption and geomechanics in hydraulic fractures on ultimate gas recovery are not clearly understood and systematically investigated. In this paper, we perform history matching with two field gas production data from Barnett Shale and Marcellus Shale, and first analyze the positive contribution of gas desorption and the negative effect of geomechanics on gas production, respectively, and then compare these two effects on gas production with the purpose of identifying which effect is dominant in the whole process of gas production. Furthermore, we numerically study the effect of gas desorption on gas recovery with available laboratory data of Langmuir isotherm from five different shale formations including Barnett Shale, New Albany Shale, Eagleford Shale, Marcellus Shale, and Haynesville Shale. Also, we use the method of Design of Experiment to perform sensitivity studies with six uncertain parameters such as reservoir permeability, bottom hole pressure, fracture conductivity, initial reservoir pressure, porosity, and fracture spacing to screen insignificant parameters and obtain critical parameters that control this process. This paper enables operators to develop an early better understanding of the effects of gas desorption and geomechanics on shale gas well performance, and provides insights into history matching and optimization of hydraulic fracturing treatment design for shale gas production.